This invention is for a rubber composition which is wear resistant and has a lowered coefficient of friction. The natural or synthetic rubber has fluorocarbon micropowder particles incorporated into the composition. A rubber with a lower coefficient of friction is a great advantage when used in applications subjecting the rubber part to wear against a metallic or hard surface. The lower coefficient of friction allows for ease in movement of the rubber part against the metal surfaces. The composition is useful as a seal between two metal surfaces that move in different directions relative to each other.
The present composition has particular application in packing elements and seals for drilling equipment and especially for large offshore oil and gas drilling equipment. Rubber packers are used in equipment associated with the equipment for delivery of oil and gas from the ocean floor to the platform floating on the ocean's surface. The rubber packers are placed between the inner barrel and outer barrel on the marine riser just below the floating platform. The platform moves with the ocean wave movement. The pipe string extends from the platform to the ocean floor and below to the producing formation. The almost constant diverse movement on the marine riser packers will reduce the usuable life of a packer to six months or less depending on drilling and sea conditions.
The rubber composition of this invention exhibits unusual resistance to wear. The rubber parts which encounter constant movement against their surfaces benefit from a reduced friction contact with the metallic surface which causes the rubber to abrade on the metallic surface. The rubber parts lose their shape and must be replaced. The improved rubber composition increases the life of the part and eliminates the down time associated with replacement. With the new rubber composition there is less abrasion because the rubber and metal tend to slide against each other. When there is some deposition of the rubber on the metal part during the movement of the riser, there will be less friction between the rubber packer and the rubber coated surface of the metal part due to the improved low friction rubber composition used in the packer.
The new composition contains a high loading of fluorocarbon micropowder of particles which have a typical diameter of less than one micron. Even with the high loading the composition can be mixed and processed with conventional equipment. The physical properties of the rubber for manufacturing purposes are not affected. The inert fluorocarbon micropowder can be used in the natural and synthetic rubbers. Another embodiment of the new composition includes using an oil which is incompatible with the rubber base stock with the fluorocarbon micropowder to comprise a friction reducing system. Also, a system can be used of a mixture of fluorocarbon particles, incompatible oil and graphite.
The rubber parts made of this invention will have a longer useful lifetime. This attribute will save expenditures in replacement parts, down-time experienced during replacement and provide a more reliable rubber part for applications in which avoiding wear on the part subjected to constant movement or motion against a metal part is desired.